Known carriers include those coated with a copolymer comprising vinylidene fluoride (hereinafter generally referred to as "VdF") and tetrafluoroethylene (hereinafter generally referred to as "TFE") (Japanese Unexamined Patent Publication No. 58-20,875). However, the copolymer in the carriers has a low solvent solubility and thus only a limited range of solvents can be used in application of the copolymer onto the carrier core composed of powders of iron, ferrite and the like. Further the copolymer can not be dissolved to a high concentration, posing the problems of entailing a low productivity and giving only thin coatings with low strength and poor adhesion to the core.
Also known are carriers coated with a VdF/TFE/vinyl butyrate copolymer (Japanese Unexamined Patent Publication No. 54-110,839). With the fluorine-free monomer present as the third component, this type of copolymer exhibits a high solvent solubility but a small electrostatic charge capacity when used for coating the carrier core.